Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description goes beyond that by disclosing the exact shape of the response and the token-savings rationale, which is genuinely useful behavioral context. It stops short of covering the L402 payment behavior, but that is documented in the schema's parameter description.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single dense sentence with the core action front-loaded and the return fields listed after. The field enumeration is long but each item carries real information for an agent; the closing token-savings claim is mild marketing but still justifies using this tool over raw parsing.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, so the description must carry the return-value burden, and it does so by enumerating every field returned. The payment flow lives in the schema, and error conditions for invalid or unknown txids are the only notable gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both the txid format and the L402 payment flow are fully documented structurally. The prose adds no syntax, format, or constraint detail beyond what the schema already provides, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (fetch) and resource (Bitcoin transaction by txid) and enumerates the returned fields: type, input/output counts, fees, fee rate, confirmation status, RBF, SegWit/Taproot flags, and agent_summary. No sibling in the list performs transaction decoding, so the differentiation gap is irrelevant here.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied: an agent infers it should call this when it has a txid and wants a decoded summary. There is no explicit when-to-use versus alternatives (e.g. when to prefer this over raw hex parsing) and no exclusions or prerequisites stated in the description itself.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.